Jan., 1889. 
spencer’s “first principles.” 
7 
sufficient warrant for a criticism of the nature of its materials 
and the strength of its supports. But this is the task I have 
undertaken. 
If I may assume that you are acquainted with Spencer’s 
argument, I need only briefly sum it up as follows :— 
In Chapter IY. he maintains that the indestructibility of 
matter is a necessary truth, one of which we cannot imagine the 
contrary when we once clearly present to our minds the mean¬ 
ing of the terms “ matter ” and “indestructible.” He argues 
that the so-called chemical and physical proofs based upon 
weighings really assume the principle in assuming that the 
weights used to counterpoise are constant in their value. 
He concludes that, when analysed, the indestructibility of 
matter is found to mean the persistence of force. For if we use 
the chemical proof, the constancy of weight means persistence 
of gravitative force, and, if we regard the principle as a 
necessary truth, we again come to persistence of force, for it 
is by force that we really know matter. 
In Chapter V. it is argued that the continuity of motion 
is a truth of the same order, one of which we cannot imagine 
the contrary. When we contemplate a swinging pendulum, 
and note the recurring appearance and disappearance of its 
motion, we cannot suppose that that of which the motion is a 
sign has been annihilated when the motion ceases at the end 
of a swing. We must suppose that there is a continuous 
existence now shown by the motion, and now by the puli down 
which we feel if we hold the pendulum in its highest position. 
This existence we think of as the objective correlative of 
muscular effort; we think of it in terms of force. Again, if a 
moving body is gradually brought to rest, it is stopped by 
force exerted by some other body or bodies upon it, and this 
retarding force has a reaction on the acting bodies, handing 
on to them the motion lost by the body as it slackens speed. 
Again we think of the motion being communicated by force. 
If we seek to prove the continuity of motion, our so called 
proofs really assume the persistence of force in some form or 
another, either in the constancy of the masses concerned, 
or in the constancy of the measuring instruments used. 
Hence we again come to the same foundation as that on 
which the indestructibility of matter is built, viz:—the 
persistence of force. 
Having concluded that the indestructibility of matter and 
the continuity of motion ultimately imply the persistence of 
force, Spencer proceeds, in Chapter VI., to examine the 
warrant we have for the truth of this last doctrine. He 
asserts that all our measures assume it, and that therefore we 
